PLC Programming

What is What in CoDeSys
2 What is What in CoDeSys
2.1 Project Components...
Project
A project contains all of the objects in a PLC program. A project is saved in a file named after the
project. The following objects are included in a project:
POUs (Program Organization Units), data types, visualizations, resources, and libraries.
POU (Program Organization Unit)
Function
Functions, function blocks, and programs are POUs which can be supplemented by actions.
Each POU consists of a declaration part and a body. The body is written in one of the IEC
programming languages which include IL, ST, SFC, FBD, LD or CFC.
CoDeSys supports all IEC standard POUs. If you want to use these POUs in your project, you must
include the library standard.lib in your project.
POUs can call up other POUs. However, recursions are not allowed.
A function is a POU, which yields exactly one data element (which can consist of several elements,
such as fields or structures) when it is processed, and whose call in textual languages can occur as
an operator in expressions.
When declaring a function do not forget that the function must receive a type. This means, after the
function name, you must enter a colon followed by a type.
A correct function declaration can look like this example:
FUNCTION Fct: INT
In addition, a result must be assigned to the function. That means that function name is used as an
output variable.
A function declaration begins with the keyword FUNCTION.
In IL a function call only can be positioned within actions of a step or within a transition.
In ST a function call can be used as operand in an expression.
Example in IL of a function that takes three input variables and returns the product of the first two
divided by the third:
Example of a function in IL
CoDeSys V2.3 2-1